Abstract
Little is known about the uptake or metabolism of essential fatty acids (EFAs) in various mammalian organs. Thus, the distribution of deuterated alpha-linolenic acid (18:3n-3) and linoleic acid (18:2n-6) and their metabolites was studied using a stable isotope tracer technique. Rats were orally administered a single dose of a mixture (20 mg each) of ethyl D5-18:3n-3 and D5-18:2n-6, and 25 tissues per animal were analyzed for D5-labeled PUFAs at 4, 8, 24, 96, 168, 240, 360, and 600 h after dosing. Plasma, stomach, and spleen contained the highest concentrations of labeled precursors at the earliest time points, whereas other internal organs and red blood cells reached their maximal concentrations at 8 h. The time-course data were consistent with liver metabolism of EFAs, but local metabolism in other tissues could not be ruled out. Brain, spinal cord, heart, testis, and eye accumulated docosahexaenoic acid with time, whereas skin accumulated mainly 20:4n-6. On average, approximately 16-18% of the D5-18:3n-3 and D5-18:2n-6 initial dosage was eventually accumulated in tissues, principally in adipose, skin, and muscle. Approximately 6.0% of D5-18:3n-3 and 2.6% of D5-18:2n-6 were elongated/desaturated and stored, mainly in muscle, adipose, and the carcass. The remaining 78% of both precursors was apparently catabolized or excreted.
Highlights
Little is known about the uptake or metabolism of essential fatty acids (EFAs) in various mammalian organs
Many studies have focused upon the liver as the primary site for essential fatty acid (EFA) metabolism in mammals, relatively little is known about other organs with respect to their uptake of EFA precursors and products or the manner in which these fatty acids are distributed to them
Efforts to understand and model human EFA metabolism depend upon a rig
Summary
Little is known about the uptake or metabolism of essential fatty acids (EFAs) in various mammalian organs. Previous investigations include stable isotope studies in primates and have provided analyses of EFA uptake and metabolism of the liver, nervous system, and blood stream [4] and, in some cases, other internal organs such as the heart, lung, and kidney [5]. It would be valuable to extend these studies to a description of EFA uptake and metabolism in all of the major tissues in mammals under well-controlled and defined dietary conditions. This information is a first step in the understanding of the EFA requirements and the ability to elaborate and use long-chain polyunsaturates of various organs and tissues throughout the body. Negative chemical ionization gas liquid chromatography-mass spectrometry (GC-MS) analysis was used for the quantification of the precursors and their individual metabolites in 25 components from 4 to 600 h after dosing
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